/**
 * 912. 排序数组
 * https://leetcode.cn/problems/sort-an-array/description/
 */
class Solution {
    int[] tmp;
    public int[] sortArray(int[] nums) {
        tmp = new int[nums.length];
        mergeSort(nums, 0, nums.length - 1);
        return nums;
    }

    public void mergeSort(int[] nums, int left, int right) {
        if(left >= right) return;

        //1、根据中间节点划分区间
        int mid = (left + right) / 2;
        //[left, mid] [mid + 1, right]

        //2、把左右区间排个序
        mergeSort(nums, left, mid);
        mergeSort(nums, mid + 1, right);

        //3、合并两个有序数组
        // int[] tmp = new int[right - left + 1];搞成全局的
        int cur1 = left, cur2 = mid + 1, i = 0;
        while(cur1 <= mid && cur2 <= right) 
            tmp[i++] = nums[cur1] <= nums[cur2] ? nums[cur1++] : nums[cur2++];
        //处理最后一个没有排序的数据
        while(cur1 <= mid) tmp[i++] = nums[cur1++];
        while(cur2 <= right) tmp[i++] = nums[cur2++];

        //4、还原
        for(int j = left; j <= right; j++) {
            nums[j] = tmp[j - left];
        }
    }
}